A typical electrical connector assembly for mounting on a printed circuit board includes a dielectric housing having a board-mounting face and a mating face, with a plurality of terminal-receiving passages extending between the faces. A plurality of terminals are received in the passages, and each terminal includes a contact section near the mating face for interengagement with a contact of a complementary mating electrical apparatus and a tail section projecting from the housing toward the printed circuit board for termination to circuit traces on the board, usually by soldering processes.
A specific type of board mounted electrical connector assembly is designed for interconnection between a first printed circuit board and one or more second printed circuit boards. The assembly is permanently mounted on or terminated to the first printed circuit board which commonly is called the "mother" board. The assembly removably receives the one or more second printed circuit boards which commonly are called the "daughter" boards. The housings for such connector assemblies are considerably elongated to accommodate an edge of the daughter board(s). Typically, the housing includes one or more slots extending lengthwise thereof, whereby the mating face of the housing forms a board-receiving face of the connector. Of course, there are other types of considerably elongated electrical connector assemblies which create certain problems as outlined below.
Specifically, the problem of printed circuit board warpage or bending is a continuing problem experienced in both the manufacture and use of printed circuit boards having elongated connectors mounted thereto. Warpage is less problematic with short or box-like connectors or components. During manufacturing processes, such as conventional soldering techniques, the printed circuit board and components and connectors are subjected to very high temperatures. Consequently, the boards are known to warp to some extent as a result of such high temperatures. Warpage or bending of a board can reduce the assurance of proper electrical connections between the connector terminals and the circuits on the board. Warpage also can interfere with placement of a plurality of circuit boards in closely spaced arrays and can even result in short circuiting between boards. As a result, warpage can and does result in costly scrapping of many circuit boards after circuit components have been connected in place. Warped boards can be difficult or impossible to insert in pre-designed racks, and, even if successfully inserted, the boards may bulge laterally to an extent that the circuit components thereon come into contact with components on a closely spaced adjacent board, ruining expensive electrical equipment.
Even during use, thin printed circuit boards can bend simply because of the weight placed on the boards or by other extraneous pressures. Again, the bent boards can damage the interconnections between the boards and the electrical components and/or connectors mounted thereon, or the boards may short circuit with adjacent closely spaced boards.
The most common expedient for eliminating the problem of printed circuit board warpage or bending is to provide "board stiffeners" which are rigid in a direction generally perpendicular to the plane of the board. In essence, these separate board stiffeners act as common mechanical support members secured to the board, such as with I-beams or L-beams in mechanical structures. Examples of separate circuit board stiffening devices or brackets are shown in U.S. Pat. Nos. 4,452,359, dated Jun. 5, 1984; 4,533,978, dated Aug. 6, 1985; 4,952,172, dated Aug. 28, 1990; 4,988,577, dated Jan. 29, 1991; 5,186,377, dated Feb. 16, 1993; and 5,198,279, dated Mar. 30, 1993.
The use of separate board stiffening devices, in turn, create other problems in the manufacture and use of printed circuit board connector systems. For instance, the separate board stiffeners use a considerable amount of valuable board "real estate" which otherwise could be used for mounting other circuit components. This creates a critical problem with the ever-increasing miniaturization of electronic circuitry. In addition, the fact that the stiffeners comprise separate mechanical components which must be mounted on and secured to the board, separate manufacturing steps are required in fabricating the circuit board assembly which, in turn, increases the manufacturing costs.
The present invention is directed to providing a printed circuit board stiffening system which solves the problems described above without using any additional printed circuit board real estate and without requiring any separate manufacturing or assembling steps in mounting the board stiffener(s) to the printed circuit board.